Flexible Rogowski coils (for example as described in U.S. Pat. No. 3,434,052) provide a convenient way of obtaining AC current measurements in hard to access or temporary current monitoring situations. In terms of accuracy they suffer from the ability to make a uniform and flexible solenoid to high precision, limiting uniformity of calibration factor within the measurement loop, and limiting the level of rejection achieved for nearby currents outside the loop. This is especially true around point where the two ends of the flexible coil are connected because space has to be allocated for insulation and mechanical clamping arrangements. Another undesired feature is the difficulty of obtaining good thermal stability in view of the flexibility of the materials defining the cross section of the coils, and the length of the loop, both of which directly affect the sensitivity of the current measurement.